Various impulse response measurement methods are accurate for Hammerstein systems but when a linear filter precedes a static non-linearity, as in a Wiener-Hammerstein system, inter-modulation distortion results in undesirable artifacts. In this paper the advantages of the wide maximum length sequence and multiple noise sequences methods are combined to create a method of measuring the diagonal Volterra series expansion of the impulse response of general nonlinear systems that may be seen as an alternative to the existing dynamic convolution method.

A discussion on pulse reflectometry which is a commonly used technique to probe cavities and materials covers implications for tube and pipe inspection; application challenges; limitations and advantages; performance results; and opportunities. This is an abstract of a paper presented at the American Fuel and Petrochemical Manufacturers Reliability and Maintenance Conference (5/22-24/2013 Orlando, FL).

Tube inspections are performed by combining the use of APR technology with GW technology. The reflections measured by both technologies are compared to each other and used to more specifically identify the type and location of a flaw or anomaly that appears in the interior of the tube. Further, embodiments of novel probes to be used in GW technique for inspecting tubes with mechanical waves having bandwidth that is equal to 150 KHz or more are disclosed.

A tube inspection system that includes a guided-wave-transducer mechanism (GWTM) that is associated with a tube that is being inspected. The GWTM can have one ring with N guided-wave transducers (GWTs) distributed thereon, and another ring with M guided-wave transducers (GWTs) distributed thereon. A controller excites mechanical waves by the GWTs of the first ring that propagate in the wall of the tube being inspected and along its axis. The M GWTs of the second ring obtain received mechanical waves and convert them to electronic signals. The M electronic signals are processed to provide a measured signal in which a wanted mode is enhanced.

A measurement systems that reduces spurious artifacts in reflected signals by generating and employing an improved maximum length sequence. Accurate acoustic measurements with both high SNR and low spurious artifacts are made possible by generating Wide MLS (WMLS) which modifies a base MLS by replacing each value with a sequence that includes the value and one or more additional values, where typically the replaced values have opposing polarities and, the additional signals have intermediate values. An exemplary intermediate values can be approximately zero value.

A system to measure the internal state of a bundle of tubes by injecting a signal into each tube of the bundle, receiving reflections from the tube due to anomalies within the tube, then analyzing the reflections to determine the type or characteristics about the anomalies. The analyzed information is stored in database to be used for statistical processing. Further, the device can be used in the performance of a cleaning process by conducting an initial assessment of the tubes in a bundle of tubes, comparing the stored data and estimating the number of cleaning cycles that will be required, and re-conducting the evaluation of the state of the tubes after every cleaning cycle or after every few cleaning cycles.